John 13:16-20 (Thursday gospel) -- I'm adding v15 for context:
15 I have given you a model to follow, so that as I have done for you, you should also do.
16 Amen, amen, I say to you, no slave is greater than his master nor any messenger greater than the one who sent him.
17 If you understand this, blessed are you if you do it.
18 I am not speaking of all of you. I know those whom I have chosen. But so that the scripture might be fulfilled, 'The one who ate my food has raised his heel against me.'
19 From now on I am telling you before it happens, so that when it happens you may believe that I AM.
20 Amen, amen, I say to you, whoever receives the one I send receives me, and whoever receives me receives the one who sent me."
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Christ had just finished washing the disciples' feet. If you look at Luke's description of the upper room (http://www.nccbuscc.org/nab/bible/luke/luke22.htm), you'll see that right after instituting the eucharist, an argument broke out among the disciples about who among them was the greatest.
Imagine how Jesus must have felt then. He gets up, strips his outer garments, and washes their feet. There had to have been silence in the room.
Peter objects. Christ rebukes him, and tells him He just gave them the model to follow (v15).
Today's reading picks up from there. He tells the Twelve that nobody is greater than He is, and that they need to understand that. Look at v19 - He tells the apostles that he is YHWH ("I AM", v19), and he just got down on his knees and washed their feet! This is the God of Abraham, Isaac, and Jacob -- the master of land and sea, the voice from the burning bush, the force that parted the Red Sea, the God that struck down the Pharoah and delivered Israel from Egypt.
He says ... be a servent.
